Cavity filled lightpipe for illuminating keys of a keyboard

ABSTRACT

A light guide is provided for illuminating innumerable constructions, but which is ideally suited for illuminating the keys of a keyboard. The light guide includes a translucent planar plate having a top, a bottom and sides. Further, the light guide includes one or more cavities which project upwardly into the translucent plate from its bottom surface. The cavities are hollow or filled with a translucent material so that the translucent plate and the one or more cavities form translucent interfaces where the cavities interface with the plate. The light guide also includes a reflector which covers the plate bottom and cavity openings. Light produced by a light source, preferably in the form of one or more LEDs, is transmitted to and through the translucent plate until striking the plate-cavity interfaces where the light is refracted into the cavities&#39; interior or reflected upwardly to the plate&#39;s upper surface. After initial refraction into a cavity, the light reflects off the reflector and travels again into the translucent plate until transmitted from the plate&#39;s upper surface. Preferably, light guide is positioned within a keyboard housing with the cavities underlying the keys so that light is transmitted from the translucent sheet to the keys.

BACKGROUND OF THE INVENTION

The present invention relates generally to light pipes, also referred toas light guides and light plates, which carry light from a light sourceto a desired area.

More specifically, the present invention relates to light pipes forkeyboards having illuminated key members.

Conventional keyboards include a plurality of key members which displaysymbols, such as alphanumeric keys, on their top surfaces. Moreover,typical modern keyboards, such as those found in cellular telephones,Automatic Teller Machines (ATMs), electric typewriters and computersutilize a make-and-break electrical circuit which is activated bydepression of a key member for identifying a particular symbol embeddedon the top of the key member.

A problem with prior art keyboards is that it is often difficult todiscern the symbol appearing on the top of the key member under poorlighting conditions. This causes the keyboard operator to memorize thekey locations or to strain their eyes to operate the keys of thekeyboard under low light conditions. This has become a much greaterproblem in present day society as keyboards have become necessary foreveryday use and as keyboard use is not limited primarily to operationby workers in business offices as in the past. As a result of thisexpansion of keyboard use, more and more operators have less training onkeyboards, and correspondingly many keyboard operators utilize a “huntand peck” style of keyboard operation.

Moreover, the advent of laptop and notebook computers has resulted inthe use of keyboards at places where they were not previously operated.Often these places provide limited light making it difficult forkeyboard operators to quickly and easily operate the keyboard. Forexample, it is a common sight on commercial aircraft to see a passengerslowly hunt and peck at their keyboards continuously looking at the keymembers to verify that they are in fact pressing the correct keys.

Accordingly, it is clear that there is a need for an apparatus thatmakes keyboard key members more discernable in low light conditions.Backlighting is commonly used in rubber keypads, membrane switches,rigid panels and the like to make them more visible and discernable.These keypad panels typically make use of light emitting crystals(LECs), light emitting diodes (LEDs), and/or fiberoptics for thispurpose. Most prior backlit keyboards utilize a light source which istypically transmitted via a fiberoptic cable to the key members of akeypad. For example, U.S. Pat. No. 5,034,602 issued to Garcia, Jr. etal. discloses an optically activated keyboard which uses fiberopticcables to transmit light to translucent key members. The light istransmitted through the translucent key members where it is emitted fromthe top of the key cap. Similarly, U.S. Pat. No. 3,886,544 issued toNarodny and U.S. Pat. No. 5,097,396 issued to Myers disclose keyboardswhich use backlighting. Each key member in connection to a fiberopticcable which transmits light to a respective key member which thereaftertransmits light from the top of the key cap. Additional keyboard andkeypad techniques include the LED and LEC backlighting commonly utilizedfor alarm activator and deactivator keypads wherein each key includes aseparate LED or LEC structure embedded in or behind the key member.Unfortunately, it is extremely difficult to route fiber optics to thekeyboard keys of today's computer systems. For example, it would beparticularly difficult to route fiberoptic cables and provide a lightsource to the key members of today's notebook computers and palm-sizedcomputer systems.

In addition, the light sources for use with prior art backlit keyboardsrequire substantial power and in some cases, a fan for cooling whichdraws additional power. These constructions are prohibitive for portablecomputers such as laptop and notebook computers which draw on the powerof a rechargeable battery and where power is at a premium.

Recently, the present named inventor, Michael Shipman, developednumerous lighted keyboard constructions which are the subject of U.S.Pat. Nos. 6,217,183; 6,467,924 and 6,918,677 and which are incorporatedby reference herein. The keyboard constructions utilize a variety ofelectro luminescent, light transmitting panels and light emitting diodes(LED) for illuminating the keys of a keyboard. For the most part, theseconstructions are satisfactory. However, electro luminescent lightsources are very expensive and the alternative constructions requireusing several LEDs to adequately and uniformly illuminate a keyboard,which by their quantity, also makes the keyboard prohibitively expensivefor mass market distribution.

Accordingly, there is a need for an improved light distributionconstruction, such as a light guide, which is less expensive thanprevious designs.

Accordingly, it would be highly advantageous to provide a light guidefor a keyboard having illuminated key members suitable for use withtoday's computer systems including portable computers.

It would also be highly advantageous to provide a keyboard havingilluminated keys which does not require routing of fiberoptic cables toeach key member.

In addition, it would be highly advantageous to provide a keyboardhaving illuminated key members which is lightweight, simple andinexpensive to manufacture, and requires low power consumption.

SUMMARY OF THE INVENTION

Briefly, in accordance with the invention, I provide an improved lightguide useful for illuminating various hardware such as dashboards,automatic teller machines (ATMs), airplane and spacecraft cockpit, etc.However, because the light guide is believed to have particularapplication to lighting the keys of keyboards, the light guide of thepresent invention is described herein with particularity forilluminating keyboards. Moreover, the term “keyboard” is intended to beinterpreted herein in a broad sense, unless specifically statedotherwise, to include any finger activated switch construction includingcomputer keyboards, calculator and cellular telephone keypads,television remote controllers, and other handheld switching devicesincluding depressable keys such as video games, GPS modules, etc.

The light guide of the present invention includes a substantially planartranslucent plate having a top, a bottom and one or more sides. Forexample, a circular light guide will have one side, a triangular lightguide will have two sides, while a light guide for illuminating akeyboard would typically be rectangular and have four sides. Preferably,but not necessarily, the plate is continuous and has no holes, or veryfew holes, which can significantly deteriorate the plate's lightcarrying properties. Moreover, the translucent plate is preferably flatand of uniform thickness. However, as understood by those skilled in theart, the plate may be curved and vary in thickness depending on designrequirements. The planar plate may be made from any number of materialssuch as glass or clear plastics including ABS, acrylics, polycarbonate,etc. In preferred embodiments, the planar plate includes sides which arecurved or rounded so as to avoid any sharp edges at the transition ofthe top or bottom with the sides which can also deteriorate the plate'slight carrying properties. Alternatively, the edge can include arecessed to form an external concavity which is preferably sized toreceive any wiring, such as wiring for any light sources.

The light guide further includes one or more cavities formed into thebottom of the planar plate. The cavities may be formed by preforming thecavities into the planar plate in an injection molding process.Alternatively, the cavities can be machined into the planar plate usingdrilling or lathe equipment. In addition, the cavities may be any numberof shapes including, but not limited to, pyramid, ellipsoid, parabolic,cone, hemispheric or cubic. Moreover, where the light guide includes aplurality of cavities, the cavities may be of different sizes anddifferent shapes.

The light guide of the present invention also includes a reflector whichunderlies the translucent plate's bottom side and which covers theplurality of cavities. Preferably, the reflector also covers thetranslucent plate's sides and upper surface, except for where light isintended to be emitted, such as under the keys of a keyboard. Thereflector may be made out of various materials such as Mylar, paper orother metals. However, it is important that the reflector include ahighly reflective surface, and thus it is preferably mirrored, white,light grey, silver, metallic silver or metallic gold so that lightstriking the reflector will reflect off the reflector as opposed to bebeing absorbed or refracted. In addition, the reflector may incorporateglowing or phosphoric elements which will emit light upon experiencinglight from another light source.

The reflector may be affixed adjacent to the translucent plate usingvarious constructions known to those skilled in the art. However, in apreferred embodiment the reflector is attached to the translucentplate's underside using an adhesive which is either highly reflective ortranslucent. Alternatively, the reflector can be positioned andmaintained in place using the overall construction of the keyboardhousing which will maintain various components in place. Screws may beused to affix the reflector and translucent plate within a desiredconstruction. However, it is preferred that the screws be reflective andof minimal size if inserted into holes formed through the reflector andtranslucent plate.

As a result of the reflector covering the cavities opening, the cavitiesare substantially sealed chambers within the planar's sheet. Formanufacturing purposes, these chambers will typically be filled withair. However, various other translucent materials may be placed withinthe cavities, such as clear or colored plastics. Alternatively, thecavities can be filled with translucent phosphoric materials which willproduce a glowing material or produce an alternative color upon lightstriking the material. Translucent plastics which produce a glowing orphosphoric appearance are sold under the generic name of “scintillatingplastics”. Where the translucent plate includes a plurality of cavities,the cavities may be filled or not filled, with a variety of materialssuch as plastics of different colors or phosphoric materials ofdifferent colors to produce light guide having points of illumination ofdifferent colors and luminosity.

The light guide of the present invention further includes a light sourcefor emitting light which is received by the translucent plate. The lightsource may be any of numerous light sources known to those skilled inthe art including electro-luminescent panels, incandescent light bulbs,light emitting diodes (LEDs) and light emitting crystals (LECs).However, for cost and efficiency, it is preferred that the light sourceof the present invention be one or more LEDs. The light sources may bepositioned in any way so as to shine light onto or into the translucentplate. For example, the light source may be positioned immediatelyadjacent to the translucent plate's edges. Alternatively, the lightsources may be positioned to project into a recess formed into thetranslucent plate's upper or lower surfaces or into the translucentplate's sides.

In operation, light is transmitted into the translucent plate. The lightis then reflected off the reflector throughout the translucent plate'sinterior until striking the interface of the translucent plate with acavity. Because of the translucent properties of both the cavity and thetranslucent plate, significant amounts of light will be transmitted fromthe translucent plate into the cavity by direct transmission or byrefraction depending upon the light's angle to the cavity's interfaceand depending on material properties. Preferably the cavity has a cone,parabolic or ellipsoid shape causing light to project downwardly tostrike the reflector. Upon striking the reflector, light is reflectedupwardly through the cavity to translucent plate's interface where lightpasses again into the translucent plate until being transmitted from thetranslucent plate's upper surface.

As would be appreciated by those skilled in the art, various factorsincluding the translucent plate's material and angle of light strikingthe sheet cavity interface will cause some light to reflect, as opposedto refract into the cavity. As a result of the cavities dome-lightshape, much of the light will be caused to reflect upwardly through theplate to be transmitted from the translucent plate's upper side. As aresult of the light reflected and refracted from the plate and cavityinterfaces, the light guide will produce one or more illuminated shapesformed on the translucent plate's upper side which correspond in sizeand placement to the underlying cavities.

Typically, the light producing cavities will be centered directly underthe keys of a keyboard. However, in an alternative preferred embodiment,the cavities are displace off-center from directly below a key member.In particular, it has been found that backwardly displacing the lightproduced under a key approximately 1-5 mm. can make the characters, alsoreferred to herein as indicia, formed on a key to appear more luminous.The amount of offset can be determined by one skilled in the art due tothe viewing angle of a person operating the keyboard and due to theplacement of characters on the key members.

The light guide of the present invention may be incorporated into thevarious keyboard constructions having illuminated indicia andilluminated key members. A few such keyboards are described as follows.A preferred keyboard includes a plurality of key members, and a lightchanneling membrane. The key members and light channeling membrane areconstructed of a substantially translucent material capable ofchanneling light rays. In addition, the keyboard of the presentinvention includes a light source optically connected to the lightchanneling membrane. In operation, the light source produces light rayswhich are received by the light channeling membrane within the keyboardhousing, or is positioned adjacent the indicia or plurality of keymembers. The light rays are channeled through the light channelingmembrane to the indicia or key members which receive the light rays attheir lower extremities and which channel the light rays upwardly totheir top surface. Light is then emitted from the top of the key memberto either provide illumination around an opaque construction of a symboldisplayed on the top surface of the key member, or in the alternative,to emit light rays in the shape of the symbol itself, as in the case ofkeyboard indicia.

In a preferred embodiment, the upper clamshell member of the keyboard'shousing acts as a light channeling membrane. The light channelingmembrane and plurality of key members are manufactured of acrylicplastic, polycarbonate or glass for optical clarity, though othermaterials may be used depending on cost, weight and manufacturinglimitations as would be understood by those skilled in the art. For thisembodiment, the light channeling membrane includes a plurality of bores,with each bore being constructed for receipt of the key shaft of acorresponding key member. Meanwhile, each key member also includes a keycap having a symbol displayed thereon. Each key member shaft isconstructed to extend downwardly and telescopically into a correspondingbore of the light channeling membrane. Light is channeled through thetranslucent material of the light channeling membrane until it isemitted from cylindrical sidewalls into the membrane's bores. Lightemitted from the bores' interior sidewalls is received onto the exteriorof the shafts of the key members and channeled upwardly through thetranslucent material of the shaft, to the key caps which are alsoconstructed of a translucent material. The key cap includes an uppersurface having an alphanumeric symbol displayed thereon which isilluminated by light passing through the shaft of the key member toprovide the desired illuminated alphanumeric symbol. The symbol can beconstructed as light emitting or as opaque with the remainder of the topsurface being conversely opaque or light emitting, depending on whetherthe desired symbol is in either a negative or a positive representationthereof.

In another preferred embodiment of the present invention, the keyboardhousing is constructed partially of a substantially translucent materialfor communicating light rays through said keyboard in the form ofindicia, wherein said indicia is discernible when light rays pass therethrough. The indicia may be an indicator or, for example, correspond toa key member or a group of key members.

The light source may take various forms known to those skilled in theart. For example, the light source may be an incandescent lightbulb,light emitting diode, light emitting crystal, etc. Moreover, the lightsource may produce light which can be selectively varied in color so asto enable the keyboard operator to alter the color of the luminescenceof the key members. For example, the light source may comprise aplurality of diodes with each diode producing different colored light.Selective activation and deactivation of the diodes alone or incombination will produce key members illuminated in different colors.

In another preferred embodiment of the present invention, the lightsource is connected to a light pipe located within the keyboard housingfor channeling light to a plurality of key members. The light pipe, alsoknown as a light guide, may be constructed in various shapes and ofvarious materials such as of lengths of acrylic plastic, polycarbonate,or glass. Alternatively, the light pipe may be constructed of one ormore fiberoptic fibers or cables. The light pipes may also beconstructed of one or more different translucent and fluorescent coloredmaterials for projecting light of one or more colors upon the keymembers, and for producing alphanumeric characters on the key members ofdifferent colors. An acceptable colored material includes “scintillatingplastic” which is typically an acrylic plastic incorporating differentcolored flourescent dyes.

Preferably, the light pipes are constructed to project light laterallyfrom their exteriors. Where the light pipes are comprised of fiberopticcables, the fiberoptic cables are also constructed to project lightlaterally from their cylindrical exterior as opposed to predominantlyfrom their distal extremities. This can be accomplished by notching,knurling, scratching or in other manners creating flaws in the otherwisesmooth exterior cylindrical surface of the fiberoptic cable. These flawshave been found to interrupt the transmission of light along the lengthof the fiberoptic cable and to transmit light laterally from theexterior surface of the fiberoptic cable, typically opposite the sidewhich has been flawed. For application with the present invention, alight pipe is routed alongside indicia or a plurality of key members.Light transmitted through the light pipe may be transmitted laterallyupon the keyshafts of the key members. The light is then channeledthrough the key members so as to be emitted from the upper surface ofthe key members to illuminate a symbol or character.

In an additional preferred embodiment of the present invention, thelight source is constructed of a substantially planar plate underlyingthe light channeling membrane of the keyboard. An alternativeconstruction for the illuminating sheet of the light source is describedin U.S. Pat. No. 5,045,755 issued to Appelberg and assigned to E-LiteTechnologies, Inc. which is incorporated herein by reference. Theilluminating sheet is a split electrode or parallel plate lampconsisting of a main body sandwiched between first and second conductivelayers. Application of an alternating current to the planar sheetprovides a luminescent sheet which can be adhesively attached to thebottom of the keyboard light channeling membrane. Moreover, theilluminating sheet is sufficiently thin as to not require significantmodification to existing computer keyboard designs.

An additional preferred construction of the luminescent sheet can beobtained from MKS, Inc. located in Bridgeton, N.J., USA under thetrademark designation QUANTAFLEX™. The QUANTAFLEX™ material is anelectroluminescent lamp including luminescent phosphors embedded in thedielectric medium of a capacitor constructed in the form of a sheet.Electrodes, including at least one translucent electrode, form the topand bottom layers of the QUANTAFLEX™ material. Upon application of analternating current to the electrodes, the phosphors give off photonsproducing light in the visible spectrum. An advantage of the QUANTAFLEX™material is that the phosphors can be selectively encapsulated betweenthe electrode layers of the luminescent sheet so as to selectivelyproduce patterns of light emitted from the luminescent sheet. Forexample, for application with the present invention, it is preferredthat the QUANTAFLEX™ material be constructed to produce light only belowand/or immediately adjacent to the key members so as to reduce powerconsumption.

In still additional preferred embodiments, the luminescent sheet isconstructed of one of the rapidly developing technologies directed toOrganic Light Emitting Devices (OLED), Transparent Organic LightEmitting Devices (TOLED), or Flexible Organic Light Emitting Devices(FOLED). Descriptions of these technologies are available to thoseskilled in the art and will not be described in further detail herein.

In an additional preferred embodiment, the luminescent sheet isconstructed of a substantially translucent material, such as an acrylicplastic, polycarbonate, epoxies and glass, connected to an independentlight source, such as light emitting diodes, light emitting crystals,etc. For this embodiment, the light channeling luminescent sheetoperates as a planar light pipe for channeling light from the lightsource to the key members. Preferably, the luminescent sheet includesreflecting and refracting bottom cavities and a reflector for focusingthe light upon the key members.

In still an additional preferred embodiment, the luminescent sheet isconstructed of a plurality of fiberoptic cables laid side by side toform a planar sheet. The ends of the cables are positioned adjacent toone or more LEDs or LECs so that emitted light is channeled through thefiberoptic cables. Again, the fiberoptic cables are notched, knurled,scratched or the smooth exterior is otherwise flawed to interrupt thetransmission of light along the length of the fiberoptic cables and totransmit light laterally from the exterior surface of the fiberoptic.

Where the keyboard of the present invention utilizes an illuminatingsheet for providing light to the key members, the illuminating sheet maybe formed with a plurality of holes. The luminescent sheet is thenaffixed below the light channeling membrane with the holes of theluminescent sheet underlining the bores projecting through the upperclamshell member of the keyboard, which may also function as a lightchanneling membrane. This construction permits the shafts of the keymembers to project through the clamshell bores and through the holes ofthe illuminating sheet. Where the keyboard is constructed for use with acomputer, disposed below the illuminating sheet is an elastic diaphragm,for biasing the key members upwardly, and a keyboard circuit board. Thecircuit board includes a plurality of switches which are closeable uponpressure application such that depression of the key members causes therespective key shafts to project downwardly through the membrane boresand illuminating sheet holes to depress the elastic diaphragm to, inturn, activate the circuit board switches. The closure of a particularcircuit board switch results in a corresponding signal being sent to thecomputer indicating that a particular key member has been depressed.

In an additional embodiment of the present invention, the planarluminescent sheet is disposed between the elastic diaphragm and circuitboard. The elastic diaphragm is manufactured of a translucent materialso that light emitted upwardly from the luminescent sheet shines uponthe bottoms of the key member shafts, and preferably upon the bottom ofthe upper clamshell member of the keyboard which is also preferablymanufactured of a translucent material. For this embodiment, the elasticdiaphragm and upper clamshell member cooperate to function as a lightchanneling membrane to transmit light from the light source to the keymembers. The light is then channeled through the key members to betransmitted from the tops of their key caps.

In still an additional embodiment of the present invention, the keyboardis constructed with the planar luminescent sheet positioned to underliethe elastic diaphragm and circuit board of the keyboard. The elasticdiaphragm and circuit board are manufactured of substantiallytranslucent materials for permitting light emitted from the luminescentsheet to project upwardly through the circuit board and elasticdiaphragm to strike the bottom extremities of the key members. It ispreferred that the upper clamshell member of the keyboard also betranslucent for channeling light rays to the sidewalls of the key membershafts. However, for this embodiment, the elastic diaphragm and circuitboard of the keyboard also function as the light channeling membrane.Light emitted from the planar sheet is channeled through the translucentmaterial of the elastic diaphragm and circuit board to the key members.The light is then transmitted through the key members to the keymember's upper surface where it is emitted from the top of the key capin the shape of a character displayed on the key cap.

In a preferred embodiment, it is preferred that the keyboard beconstructed or coated with an opaque material in the interstitialregions between the key members so that light does not project upwardlybetween the key members which would cause visual glare to the keyboardoperator or which would otherwise detract from the relative luminescenceof the symbols displayed on each of the key members.

Preferably, substantial portions of the keyboard and key members arecoated on their exterior surfaces with a reflective opaque coating suchas paint or the like where light is not intended to be emitted fromtheir exteriors. More particularly, it is preferred that the key membersand upper clamshell member are coated with a reflective paint forreflecting visible light, which would ordinarily be emitted from the keymembers and upper clamshell member or substantially absorbed by asubstantially non-reflective material. Thus, traditional non-reflectivepaints and coatings such as dark grey, black or blue are preferablyavoided. Meanwhile, diffuse reflective coatings such as light grey,white, and silver are preferred, as are coherent reflective coatingssuch as metallic silver, metallic gold and other shiny metallic colors.Alternative substantially reflective coatings can be selected by thoseskilled in the art without undue experimentation. In practice, much ofthe visible light, which would ordinarily be lost, is reflected ineither a diffuse or coherent manner back into the upper clamshell memberor key members until projected from the tops of the key caps to provideenhanced luminosity of the characters formed on the key caps.

In still an additional preferred embodiment, the key caps and clamshellmember include two coatings of paint or the like. The initial firstcoating utilizes a highly reflective coating, such as appearing lightgrey, white, silver, and metallic coatings such as silver, gold andother shiny metallic colors, to reduce light absorption and reflect thevisible light back into the translucent material until transmitted fromthe key caps. Meanwhile, a second coating of an alternative paint orother material is applied over the first coating. The second coating mayalso be reflective. However, it is preferred that the second coating isless reflective of visible light than the first coating, and preferablyis a substantially non-reflective dark dull color such as dark grey,black or blue.

Accordingly, it is an object of the present invention to provide animproved light distribution construction, such as a light guide, whichis less expensive than previous designs.

It is an object of the present invention to provide a light guide thatcan be incorporated into a wide variety of products including, but notlimited to, dashboards, automatic teller machines (ATMs), airplane andspacecraft cockpit, calculator and cellular telephone keypads,television remote controllers, video games and GPS modules, etc.

It is also an object of the invention to provide a light guide for akeyboards having illuminated key members suitable for use with today'scomputer systems including portable computers.

It is thus an object of the present invention to provide an inexpensiveand simple way to construct a keyboard having illuminating indicia orkeys.

It is also an object of the present invention to provide a keyboardhaving illuminated indicia or key members suitable for use with today'scomputer systems including portable computers.

Moreover, it is an object of the present invention to provide a keyboardhaving illuminated indicia or key members which does not require routingof fiberoptic cables to each key member.

These and other and more specific objects and advantages of theinvention will be apparent to those skilled in the art from thefollowing detailed description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a computer including the keyboard of theprior art;

FIG. 2 is a cutaway view of the keyboard shown in FIG. 1;

FIG. 3 is a perspective view of a preferred embodiment of a key memberfor use with the keyboard having illuminated keys of the presentinvention;

FIG. 4 is a perspective cutaway view of the translucent light channelingmembrane for use with the keyboard having illuminated keys of thepresent invention illustrating a light source as an LED or LECcomponent;

FIG. 5 is a perspective cutaway view of the translucent light channelingmembrane for use with the keyboard having illuminated keys of thepresent invention illustrating a light source as one or more fiberopticcables embedded in the translucent light channeling membrane;

FIG. 6 is a cutaway view of a preferred keyboard having illuminated keysof the present invention wherein the light source is a planarilluminating sheet underlying the light channeling membrane of thekeyboard;

FIG. 7 is an exploded view of the keyboard having illuminated keys ofthe present invention in which the light source is a planar illuminatingsheet underlying the light channeling membrane of the keyboard;

FIG. 8 is a cutaway view of a preferred keyboard having illuminated keysof the present invention wherein the light source is a planarilluminating sheet underlying the diaphragm and circuit board of thekeyboard;

FIG. 9 is an exploded view of the keyboard having illuminated keys ofthe present invention in which the light source is a planar illuminatingsheet underlying the diaphragm and the circuit board of the keyboard;

FIG. 10 is an exploded view of the keyboard having illuminated keys ofthe present invention in which the light source is a planar illuminatingsheet positioned between the elastic diaphragm and circuit board of thekeyboard;

FIG. 11 is a perspective exploded view of a preferred keyboard in whicha cylindrical light pipe is positioned adjacent to the clamshellsidewall for transmitting light upon the side of the key shaft of a keymember;

FIG. 12 is a side cut-away exploded view of the keyboard shown in FIG.11 in which light pipes are positioned adjacent to two rows ofdownwardly projecting clamshell sidewalls for transmitting light uponthe sides of a plurality of key shafts for illuminating a plurality ofkey members;

FIG. 13 is a top perspective view of a top clamshell member in which alight pipe is embedded therein for transmitting light adjacently uponthe sides of a plurality of keys for illuminating a plurality of keymembers;

FIG. 14 is an exploded view of a keyboard having illuminated indicia inwhich the light source is a planar illuminating sheet positioned belowthe elastic diaphragm and circuit board of the keyboard;

FIG. 15 is a cross-sectional view of a keyboard having illuminatedindicia and illuminated key members whereby a light source is a lightpipe positioned lateral to the key member and below the keyboard's upperclamshell member;

FIG. 16 is a to view of a keyboard having illuminated indicia whereinthe space bar includes a luminescent line extending laterally across thekey member;

FIG. 17 is a to view of a keyboard having illuminated indicia whereinthe space bar includes a luminescent decorative design in the form of acompany trademark extending laterally across the key member.

FIG. 18 is a bottom perspective view of a light guide of the presentinvention which can be incorporated into a wide variety of illuminatedstructures;

FIG. 19 is a top perspective view of a light guide of the presentinvention which can be incorporated into a wide variety of illuminatedstructures;

FIG. 20 is a top plan view of a light guide of the present inventionwhich includes various modifications for increasing light transmissionthrough the translucent sheet;

FIG. 21 is a side exploded cut-away view illustrating a light guide ofthe present invention;

FIG. 22 is a side cut-away view illustrating a light guide of thepresent invention of FIG. 21;

FIG. 23 is a side cut-away view illustrating a keyboard and light guideof the present invention including a reflector which covers the top,bottom and sides of the translucent plate; and

FIG. 24 is a side cut-away view illustrating a membrane switch keyboardand light guide of the present invention including a reflector whichcovers the bottom and sides of the translucent plate.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

While the present invention is susceptible of embodiment in variousforms, as shown in the drawings, hereinafter will be described thepresently preferred embodiments of the invention with the understandingthat the present disclosure is to be considered as an exemplification ofthe invention, and is not intended to limit the invention to specificembodiments illustrated.

With reference to FIGS. 18-24, the light guide 49, also referred toherein as a luminescent planar sheet, includes a translucent plate 71constructed in any number of shapes and sizes, but which is preferablyconstructed to have an elongate rectangular cross-section so as to havea top 73, bottom 75 and four sides 77. The translucent plate may be madeof any of the numerous light-transmitting materials, but which ispreferably made of an acrylic or polycarbonate material for cost andweight reasons. The plate further includes one or more cavity 79 whichare recesses which project upwardly from the translucent plate's bottomsurface 75 towards the interior of the translucent plate. The cavitiesmay be of any shape. However, they are preferably hemispherically orelliptically dome-shaped so as to appear circular when looked upon fromthe plate's upper side. The cavities may be entirely empty except forair. Alternatively, the cavities may be filled with a translucent orentirely transparent material. Alternatively, the material in the cavitymay be colored and may be independently light producing, such as byincluding a phosphoric component which will tend to glow upon contactwith light, even light out of the visual spectrum. Of importance, thetranslucent plate and one or more cavities form a plate-cavity interface81 which, due to material properties and the curvature of the interface,will cause light to both reflect and refract when striking the interface81.

The light guide 49 of the present invention further includes a reflector83. The reflector is positioned to cover the translucent plate'sunderside as well as cover the bottom of the cavities 79. As shown inFIGS. 21-24, the reflector may also cover the sides 77 of thetranslucent plate. Moreover, the reflector may cover the translucentplate's upper surface, except for where holes 84 are formed directlyover the light guides' cavities 79. The reflector includes a highlyreflective surface, and thus it is preferably mirrored, white, lightgrey, silver, metallic silver or metallic gold so that light strikingthe reflector will reflect off the reflector as opposed to be beingabsorbed or refracted. In addition, the reflector may incorporateglowing or phosphoric elements which will emit light upon experiencinglight from another light source.

As shown in FIGS. 20-24, the light guide also includes one or more lightsources 85, which are preferably LEDs. The LEDs are preferablypositioned to project into recesses formed in the light guide's sides ortop or bottom surfaces, as shown in FIG. 20. Alternatively, the lightsources must be positioned near enough to the translucent plate so thatlight is received within its interior.

With reference to FIGS. 21 & 22, light rays 87 are transmitted into andthrough the translucent plate 71 by LEDs 85. Thereafter, the light rayswill tend to reflect off the translucent plate's top and bottom surfacesand sides, preferably with little absorption or loss as a result of areflector 83 covering these regions, until the light strikes theplate-cavity interfaces 81. Depending on the angle of incidence betweenthe light rays 87 and plate-cavity interfaces 81, and depending onvarious other factors such as the nature of the light, the material ofthe translucent plate and the possible presence of material within thecavity, the light will either reflect from the interface or refract intothe cavity. As a result of its dome-like shape, the refracted light 87 awill refract, in other words bend, downwardly through the cavity 79until striking and reflecting off the reflector 83. The originallyrefracted and now reflected light will again refract into thetranslucent plate until it is transmitted from the translucent plate'stop 73. Meanwhile, as a result of the cavities preferably dome-likeshape, the reflected light 87 b will also be directed upwardly untilbeing transmitted from the translucent plate's upper surface immediatelyabove the cavity 79.

The reflection and refraction properties of the plate-cavity interfacecan be modified as can be determined by those skilled in the art. Forexample, polishing or roughening the plate cavity interface, such as bymachining or sand blasting, can alter the refraction and reflectionproperties until optimal light transmission from the translucent plate'supper surface is obtained.

In addition to the traditional rectangular shape of the light guideshown in FIGS. 18-19, the light guide 49 may be modified to increase thetransmission of light to areas of the light guide which are undesirablydim. For example, as shown in FIG. 20, one or more of the light guide'scorners 93 may be rounded to reduce light loss that can occur in a sharpangled corner. In addition, one or more of the corner's 97 can betruncated at various angles to direct light to different regions of thelight guide. In operation, and shown in FIG. 20, light rays emitted fromLED's can be reflected off a truncated corner to far away areas of thekeyboard where an LED is not in the vicinity. In addition to rounding ortruncating the light guide's corners, the light guide can be machined ormolded to include reflecting cut-outs 95, which can be in variousshapes, for directing light to desired areas. For example, still withreference to FIG. 20, light transmitted from one side of light guide canbe reflected with a “V” shaped cutout 95 to distribute light to farcorners of the keyboard. Moreover, a cutout 95 can be used for placementor angling of the LEDs in order to emit light more uniformly within thelight guide.

Still additional modifications can be made to edge of the translucentsheet 71 to increase light transmission. For example, in a firstembodiment, the edge is curved or rounded to provide a smooth exteriorwith no sharp edges so as to reduce light loss in a corner.Alternatively, as shown in FIGS. 18, 19 & 21-24, the edge is machined ormolded to include a recess sized for receipt of any wires 91 used forsupplying power to light sources 85. For this embodiment, it ispreferred that any wires positioned within the edge recess be coatedwith a reflective material such as white paint or white plasticinsulator. As shown in FIGS. 22-24, the reflector 83 may be positionedto cover the wire 91 to maintain it in place, and to reflect any lightback into the interior of the translucent plate 71 that otherwise mightescape.

As explained in much greater detail below, the light guide 49 of thepresent invention will have application for illuminating variousstructures, and particularly for illuminating the keys of a keyboard.For example, FIG. 23 illustrates a simplified keyboard having aplurality of keys members 11 and a translucent printed circuit board 21.Though not shown, the keyboard may include an upper clam shell member, alower clam shell member, and a preferably translucent biasing means,such as an elastomeric diaphragm, for biasing the keys upward. The lightsource 85 emits light into the translucent plate 71 where it isreflected until striking the plate-cavity interface 81. Light is thenreflected and refracted in the manner described above until beingtransmitted upwardly to the keys 11. As shown, the keyboard preferablyincludes an upper reflector 83 for further trapping the light untiltransmission to the key members through holes 84. As shown in FIG. 24,the light guide 49 of the present invention is also suitable forilluminating the keys for keyboards which incorporate membrane switchtechnology in which the circuit board 21 incorporates a plurality offlexible buttons which upon depression, activates a key. Membrane switchkeyboards are commonly used for cellular telephones, remote controllers,ATM machines, etc.

As shown in FIGS. 23 and 24, the light producing cavities can becentered directly under the keys of a keyboard. However, alternatively,the cavities may be displaced off-center from directly below a keymember. In particular, it has been found that displacing the lightproduced by the cavity 79 under a key approximately 1-5 millimeters canmake the key characters, depending on their size and placement, toappear more luminous. Moreover, displacement of the cavities relative tothe center of the key may be of particular importance where charactersare offset from the center of the key, such as for function or numberkeys, or keys having multiple different characters such as the keyboardkey showing a “!” and “1”. Moreover, key members at the top of akeyboard are typically viewed at a greater angle to vertical than keysat the bottom of a keyboard. As a result in this change in angle, it hasbeen found that displacing the light produced by the cavities 79rearwardly for keys positioned toward the back of the keyboard willincrease the apparent luminosity of the key characters. Thus, in a firstembodiment, the light produced by the cavities 79 under the lower keysincluding shift, ctrl, spacebar and letters in the rows corresponding toz, x, c, a, s, d, etc. are not displaced relative to the key membercenter. However, the cavities, and light produced by them, are displacedrearwardly in keys at the top of the keyboard such as the function keysand number keys. In still an additional embodiment, the displacement ofthe cavities, and the light produced by them, increases incrementallyfrom the bottom of the keyboard toward the top of the keyboard. Thus, asbut an example, there may be no displacement of the cavities at thebottom row of the keyboard, but the cavities may be displaced rearwardly1 millimeter in the second row from the bottom, 2 millimeters in thethird row from the bottom, 3 millimeters in the fourth row from thebottom, etc. As would be understood by those skilled in the art, thedisplacement of the light produced under keys can be applied to lightguides and light sources other than those described herein.

The light guide of the present invention is ideal for illuminating thekeys members of many additional keyboard constructions as describedbelow. Referring to FIGS. 1-3, keyboards are required to operatenumerous apparatus including computers, typewriters and personalorganizers, as well as aircraft and vehicular instrument panels. Atypical prior art keyboard 7 is shown in FIG. 1 for use with a computer3. The computer 3 also includes a central processing unit 9 and monitor5. By pressing key members 11 on the keyboard 7, one sends signals tothe central processing unit 9 instructing the computer 3 to performvarious functions.

As shown in FIG. 2, a typical keyboard 7 includes a housing 13comprising an upper clamshell member 15 and lower clamshell member 17.The keyboard 7 further includes a plurality of key members 11 and adiaphragm 19 having elastic diaphragm projections 20 for biasing the keymembers 11 to a normally upward position. A typical computer keyboard 7further includes a circuit board 21 which is disposed below the keymembers 11 and diaphragm 19. The circuit board 21 includes first andsecond printed wiring layers 23 and 27 which include engraved orembedded electrical circuits. The printed wiring layers 23 and 27 areseparated by an insulator or dielectric layer 25. The insulator layer 25includes a plurality of holes so that depression downwardly of the keymembers 11 causes the diaphragm projection 20 to be forced downwardlyupon the upper printed wiring layer 23 so that the printed wiring layers23 and 27 can come in contact to open and close distinctive electricalswitches through the holes of the insulator layer 25. Each of theseelectrical switches correspond to different key members 11 so that thekeyboard operator can depress the key members either individually or incombination to send various signals to the computer's central processingunit 9.

With reference to FIGS. 3-7, a keyboard 1 is provided having illuminatedkey members 11. Each key member 11 includes a key shaft 29 and a key cap31. Displayed on the top surface 33 of the key cap 31 is a symbol 35such as an alphanumeric character. For application of the keyboard 1 ofthe present invention, the key member 11 is constructed at leastpartially of a substantially translucent light channeling material sothat light can be received by the outer surfaces of the key shaft 29 andchanneled upwardly to be emitted from the key cap's upper surface 33. Ina first embodiment, light rays are emitted from the symbol 35 itself inwhich the translucent material portion of the key cap 31 extends throughthe key shaft 29 and key cap 31 to the key symbol 35. The remainingportion of the key cap's upper surface 33 is constructed of a non-lightemitting material or covered by an opaque coating 51 (FIG. 3). In thealternative, the entire key cap 31 including upper surface 33 isconstructed of a translucent light emitting material while the symbol 35is formed of a non-light emitting material, depending whether the symbol35 is intended to be displayed as a negative or positive representation.

With reference to FIGS. 4-7, preferably, the keyboard 1 of the presentinvention includes a light channeling membrane 37. The light channelingmembrane 37 underlies the key members 11 and is constructed to channellight rays 53 from a light source to the key shafts 29 of the keymembers 11, which in turn channel the light rays 53 along the length ofthe key shafts 29 to the key cap's upper surfaces 33. As shown in FIGS.6 and 7, the light channeling membrane 37 is incorporated into the upperclamshell portion 15 of the keyboard's housing 13. This is accomplishedby constructing the upper clamshell member 15 at least partially of atranslucent light channeling material. Light rays 53 received upon thelight channeling membrane's 37 outer surface are channeled throughoutthe translucent material to the key members 11. Preferably, the uppersurface of the light channeling membrane 37 is coated or otherwiseconstructed with an opaque coating 51 so that only the upper surfaces 33of the key members 11 are seen to illuminate by the keyboard operator.As shown in FIGS. 6 and 7, in a preferred embodiment, the lightchanneling membrane 37 includes a plurality of hollow projections 39having central longitudinal bores 41 configured for receipt of the keyshafts 29 of the key members 11. The hollow projections 39 may projectupwardly as shown in FIGS. 4-10, or may project downwardly as shown inFIGS. 11-13, and 15. Preferably, the keyboard 1 also includes adiaphragm 19 having a plurality of elastic projections 20 for biasingthe key members 11 upwardly.

In addition to the specially constructed key members 11 and lightchanneling membrane 37, the keyboard 1 of the present invention includesa light source. The light source may be embedded in, positionedalongside, or positioned underneath the light channeling membrane tocommunicate light to the light channeling membrane 37. As shown in FIG.4, in a first embodiment, the light source is comprised of one or morelight strips 45 which can be either light emitting diodes (LED) or lightemitting crystals (LEC) systems or other constructions known to thoseskilled in the art which emit light into (as shown in FIG. 5), or uponthe exterior side or bottom surfaces of the light channeling membrane37. With reference to FIGS. 5 and 11-13, in a second embodiment, thelight source is connected to one or more light pipes 47, such asfiberoptic cables, which are constructed to project light laterallyalong their length. In particular, it has been found that fiberopticcables 47 provide a highly luminescent surface where the curvedcylindrical surface has been notched, knurled, scratched or otherwiseflawed so that the flaws receive light rays from the interior of thefiberoptic cables 47 and emit those light rays laterally from thefiberoptic cable's exterior surface. For application with the presentinvention, the light pipes 47 are routed alongside, below or embedded inthe upper clamshell member 15, which is preferably at least partiallytranslucent so that light rays 53 channeled from the outer surface ofthe light pipe 47 is received by the translucent material and channeledwithin the translucent region 43 to the key members 11.

For example, as shown in FIGS. 11-13, a light pipe 47 is positionedadjacent to a plurality of key members 11, so that a single light pipecan be used to illuminate a plurality of key members. Again, the lightpipe 47 may be constructed of various materials in various shapes as canbe determined by those skilled in the art. As shown in the figures, thelight pipe 47 is attached to, or formed integral with, the upperclamshell member 15, adjacent the hollow projections 39. Preferably, thehollow projections 39 are constructed to include a portion that is atleast partially translucent to allow light channeled by the light pipe47 to channel into the bores 41 formed by the hollow projections 39 andonto the key shafts 29 of the key members 11. Alternatively, the hollowprojections 39 have openings (not shown) in their sidewalls to allowlight to project laterally from the light pipe 47 through the openingsand onto the exterior of the key shafts 29 of the key members 11. Thelight channeled by the light pipe 47 strikes the sides of the key shafts29 and is transmitted through the translucent material of the key member11 to be projected from the top of the key cap 31 in the form of analphanumeric character 35. Where the keyboard is constructed with anelastic diaphragm 19 having elastic projections 20 which project intothe bores 41 formed by the hollow projections, preferably, the elasticprojections 20 are also constructed of a translucent material so thatthe elastic projections do not impede the transmission of light from thelight pipe 47 to the key members 11 prior to depression of the keymembers.

In another preferred embodiment of the invention, the light source isconstructed as a substantially planar sheet 49 affixed below the bottomsurface of the light channeling membrane 37. Luminescent planar sheetscan be constructed by those skilled in the art using varioustechnologies. For example, the luminescent planar sheets may beconstructed of an electro luminescent lamp, an Organic Light EmittingDevice (OLED), a Transparent Organic Light Emitting Device (TOLED), or aFlexible Organic Light Emitting Device (FOLED). Alternatively, theluminescent sheet may be constructed of a substantially translucentmaterial which acts as a “light pipe” connected to an independent lightsource such a fiberoptic light source, light emitting diodes, or lightemitting crystals. In still an additional embodiment, the luminescentsheet is constructed of a plurality of fiberoptic strands laidside-by-side to form a sheet which connects to an independent lightsource such as light emitting diodes or light emitting crystals. Thetranslucent material channels the light from the light source to thekeys, or to a separate light channeling membrane 37 to illuminate thekeys.

As shown in FIGS. 6 and 7, in one of the preferred embodiments, theplanar sheet 49 is constructed with a plurality of holes 50 whichunderlie the conical projections 39 and longitudinally extending bores41 of the light channeling membrane 37. A shown in FIG. 7, thisconstruction permits the key shafts 29 of the key members 11 totelescope downwardly into the bores 41 and through the holes 50 of theluminescent sheet 49. Though the key members 11 are normally biasedupwardly by the elastomeric projections 20 of the diaphragm 19, downwarddepression of the key members 11 by fingertip pressure on the keymember's upper surfaces 33 causes the key shafts 29 to projectdownwardly through bores 41 and holes 50 until the bottom extremity ofthe key member 11 forces the diaphragm projections 20 to forcibly closeelectrical switches 55 in the circuit board 21.

With reference to FIGS. 8 and 9, in an additional preferred embodiment,the planar luminescent sheet 49 underlies both the diaphragm 19 and thecircuit board 21. The diaphragm and circuit board are constructed to besubstantially translucent, and light emitted upwardly by the luminescentplanar sheet 49 is transmitted through the translucent diaphragm andcircuit board to the bottom of the key members 11. Because the keymembers are also manufactured of a translucent material, the light isthen channeled through the key members' shafts 29 to be emitted from thekey's upper surface 33 in the form of a symbol 35. For reasons of cost,a presently preferred planar luminescent sheet for use with thisembodiment is constructed of a plurality of fiberoptic strands laidside-by-side to form a sheet. The fiber optic sheet is connected to anindependent light source such as light emitting diodes or light emittingcrystals.

With reference also to FIGS. 6 and 7, this embodiment has the benefit ofnot requiring that the upper clamshell member 15 of the keyboard bemanufactured of a translucent material so as to function as a lightchanneling membrane 37. Instead, the translucent circuit board 21 anddiaphragm 19 operate as a light channeling membrane by communicatinglight emitted by the planar sheet 49 to the bottom extremities of thekey members 11. Light is then emitted from the upper surfaces 33 of thekey members. Also with reference to FIGS. 6 and 7, this embodiment alsohas the benefit of not requiring that the luminescent planar sheet 49 beformed with holes 50 underlying each of the key members for permittingthe shafts 29 of the key members to project downwardly through the holesso as to engage the diaphragm 19 and circuit board 21. Instead, thekeyboard is constructed with the luminescent planar sheet positioned soas to avoid contact with the moving members of the keyboard, the keymembers and diaphragm. For this embodiment of the present invention, itis preferred that the luminescent planar sheet not include any holes sothat the luminescent planar sheet can provide a maximum of luminosity tothe key members.

With reference also to FIG. 10, in an additional embodiment of thepresent invention, the light source 49 is positioned between thediaphragm and circuit board. The light source is again constructed inplanar form having at least its top side providing luminescence. Theelastic diaphragm is manufactured of a translucent material so thatlight emitted upwardly from the light source, in the form of aluminescent sheet 49, shines through the diaphragm projections 20 andupon the bottoms of the key member shafts 11. Preferably, for thisembodiment, the upper clamshell member of the keyboard is alsopreferably manufactured of a translucent material so that light emittedfrom the luminescent sheet strikes the underside of the upper clamshellmember and is channeled to the sidewalls of the key members. For thisembodiment, the elastic diaphragm and upper clamshell member cooperateto function as a light channeling membrane, transmitting light from thelight source to the key members 11. The light is then channeled throughthe key members to be transmitted from the tops 33 of the key caps 31.

This embodiment has the advantage over the previous embodiment in thatlight emitted from the light source is not transmitted through thecircuit board prior to striking the outer surfaces of the key members 11which could cause diminished luminescence from the key members due tolight reflection, refraction or absorption caused by the opticalproperties of the circuit board. However, this embodiment has thedisadvantage over the prior described embodiment in that the lightsource is positioned between the key members and the circuit board. Thisconstruction requires that the light source be compressed with eachactuation of the keyboard key members unless the light source isconstructed with holes to permit the key members to engage the circuitboard directly which would also diminish the amount of light emittedfrom the key members. Though troublesome, this disadvantage can beovercome using the above described material from MKS, Inc. which it isbelieved can withstand the cyclic compression stemming from theactuations of the key members.

With reference to FIGS. 14 and 15, in still an additional embodiment ofthe invention, the keyboard's upper clamshell member includesilluminated indicia for identifying the function of one or more keymembers. Sometimes key members are too small for including symbols whichare sufficiently large so as to be easily read by a keyboard operator.This is particularly true of the “function” keys which are often foundat the top of a typical keyboard. These function keys include thetraditional “F1-F12” keys, as well as “insert”, “home”, “delete”, “end”,“page up” and “page down” keys. Further, more and more keyboards areconstructed to include “interne” keys which provide access to particularwebsites, and audio and video keys which control a computer's audio andvideo functions. In addition, keyboards are being constructed with moreand more function keys, and the invention is not intended to be limitedto the use of the function keys identified herein.

Unfortunately, these “function” keys are often constructed smaller thanthe “qwerty” letter keys. Due to their small size, it is often difficultto incorporate a symbol, or indicia, on the key members which can beeasily read by the keyboard operator. Moreover, incorporating anilluminated symbol on these keys in accordance with FIGS. 4-13 can makethe symbol even more difficult to read.

In order to overcome these disadvantages, in a preferred embodiment ofthe invention, the keyboard's upper clamshell member is constructed toinclude a region that is partially translucent. This region, constructedof a substantially translucent material, communicates light rays throughthe keyboard to display indicia indicating functions of one or moremembers. In similar fashion to the illumination of symbols shown inFIGS. 3 and 11, the clamshell indicia may be illuminated by lightchanneling through the upper clamshell to be emitted in the form of theindicia wherein an opaque coating or material is used to restrict thelight to the shape of the indicia 57. Alternatively, larger portions ofthe clamshell member 15 can be illuminated while the symbol 57 remainsopaque, depending on whether the symbol is intended to be illuminated asa positive or negative representation.

Moreover, the clamshell indicia may be illuminated using an illuminatingplanar sheet as shown in FIGS. 7-10, or the clamshell indicia may beilluminated using a light pipe as shown in FIGS. 11-13. For example, asshown in FIG. 14, in a first embodiment, the keyboard includes adiaphragm 19, first and second printed wiring layers 23 and 27, aninsulator or dielectric layer 25, and a light channeling structureconstructed as a substantially planar sheet 49. A light source 59, suchas an LED, is provided for emitting light upwardly from the planar sheet49, through the printed circuit board and elastic diaphragm so as tostrike the underside of the upper clamshell member 15. The upperclamshell member includes translucent regions 57 to provide illuminatedindicia for identifying the functions of the adjacent key members 11.

In an additional embodiment, a light pipe 47 is utilized to illuminatethe clamshell indicia 57 and key members. As shown in FIG. 15, theindica 57 reading “ORTS” is a portion of the complete word “SPORTS” foridentifying the internet function of a key member 11 which providesaccess to an internet website dedicated to sports. The keyboard includesa clamshell member 15, illuminated indicia 57, key members 11,illuminated symbols 35, a biasing projection 20 and a light pipe 47. Thelight pipe 47 is attached to, or formed integral with, the upperclamshell member 15, adjacent to the hollow projections 39. The surfaceof the light pipe 47 is scratched or otherwise flawed so as to reflectlight rays from the interior of the light pipe 47 to be emitted from thelight pipe's 47 exterior surface. Light is emitted upwardly so as toilluminate the translucent regions 57 of the upper clamshell member.

With reference also to FIGS. 11-15, preferably light is also emittedlaterally from the light pipe so as to strike the hollow projections 39.Preferably, the hollow projections 39 are constructed to include aportion that is at least partially translucent to allow light channeledby the light pipe 47 to project into the bores onto the key shafts 29 ofthe key members 11. Alternatively, the hollow projections 39 haveopenings (not shown) in their sidewalls to allow light to projectlaterally from the light pipe 47 through the openings and onto theexterior of the key shafts 29 of the key members 11. The light channeledby the light pipe 47 strikes the sides of the key shafts 29 and istransmitted through the translucent material of the key member 11 to beprojected from the top of the key cap 31 in the form of a symbol 35.

The keyboard including illuminated clamshell indicia has been describedprimarily for use in connection with illuminating and identifyingfunction keys. However, the invention is not intended to be limitedthereto. For example, a keyboard having an upper clamshell memberincluding illuminated indicia for identifying the “qwerty” key membersis also within the scope of the invention.

Preferably, the key members are also constructed, at least partially, ofa translucent material so that the key members illuminate. The keymembers may be constructed in various ways. For example, the keys may besubstantially translucent with minimal coating except for symbols, suchas letters on the keys, to provide a highly luminous key. However,preferably the keys are constructed in opposite manner in which the keysare substantially covered by an opaque material except for the symbolsto provide key members including illuminated symbols for identifyingtheir function. Where the key members are too small for readablemarkings, preferably the key members include an illuminated region, suchas in the shape of a circle or star, for providing an indication as tothe location of the key members.

In a preferred embodiment of the invention, translucent portions of thekeyboard are coated on their exterior surfaces with a reflective opaquecoating where light is not intended to be emitted. More particularly, itis preferred that the key members are coated with a paint such as lightgrey, white, silver, metallic silver, metallic gold, and other shinymetallic colors which substantially reflects visible light. Where theupper clamshell member is constructed of a translucent material, it isalso preferred that the upper clamshell be coated with a material forreflecting visible light and reducing light absorption.

Though not shown in the figures, in still an additional preferredembodiment, the key caps and clamshell member include two layers ofpaint or the like. The initial first coating is a highly reflectivematerial to reduce visible light absorption and reflect the light backinto the translucent material until transmitted from the key caps.Meanwhile, a second coating of an alternative paint or other material isapplied over the first coating. The second coating may also bereflective of visible light. However, it is preferred that the secondcoating reflects less visible light than the first coating, andpreferably the second coating is a substantially non-reflective coatingor color such as dark grey, black or blue. The keys can be made bysequentially application of coatings to translucent key members. Thesymbols, such as letters, are then formed on top of the key caps byusing a laser or the like to cut away the excess material of both thefirst and second coatings to form the desired symbols. Key members arethus produced which include an enhanced contrast between the luminescentsymbol and the substantially non-reflective regions of the key cap toprovide enhanced readability for the keyboard user.

Luminescent keyboards have been created with luminescent key caps andopaque lettering, as well as their visual negative, opaque key caps withluminescent letters 35 such as illustrated in FIGS. 3-6. Keyboards withopaque key caps and luminescent letters are considered visuallypreferable. Unfortunately, this construction does not provide aluminescent indicator for the location of the space bar, and personsworking in dark environments are not provided an indication as to theplacement of the space bar. More specifically, all keys of a traditionalkeyboard, except for the space bar, include visual indicia identifyingthe function and placement of the key member. Even recently introduced“function” keys and Internet keys, typically include visual indiciawhich can be illuminated for identifying key functions and placement.However, the space bar does not have an accepted symbol or identifierfor indicating its function, so prior art luminescent keyboards withopaque keys caps and luminescent letters have left the space barcompletely opaque. This is particularly problematic because the spacebar is the largest key member of a traditional keyboard, and people tendto look for this key member first when placing their fingers on akeyboard. This has not been a problem for key boards which haveincorporated luminescent key caps and opaque letters as manufacturershave simply illuminated the entire space bar.

With reference to FIG. 16, a preferred keyboard with opaque key caps andluminescent letters includes a space bar 61 with a luminescent line 63extending laterally across the top face of the space bar for indicatingthe space bar's function and position. The line may be dotted or dashed.Moreover, a plurality of laterally extending lines may be providedacross the face of the space bar. However, as shown in FIG. 16, a singlecontinuous luminescent line 63 is considered preferable.

As shown in FIG. 17, in an alternative embodiment of the invention forilluminating the space bar 61, the space bar includes a luminescentdecorative design 65 for indicating the space bar's position.Preferably, and as illustrated in FIG. 17, the decorative design 65 isprovided in the form of a manufacturer's or distributor's logo ortrademark. As the largest key member of a traditional keyboard, andbecause the space bar does not include an accepted indicia forindicating its function, the space bar provides an ideal size andlocation for placement of a company's logo or design.

The present invention provides for an inexpensive and simple way tomanufacture keyboards including illuminated indicia and keys havingilluminated upper surfaces. The keyboard of the present invention isparticularly suitable for use with computers and particularly withlaptop computers, though it is not intended that the present inventionbe limited thereto. While several particular forms of the invention havebeen illustrated and described, it will be apparent that variousmodifications can be made without departing from the spirit and scope ofthe invention. Accordingly, it is not intended that the invention belimited except by the following claims.

We claim:
 1. A light guide comprising: an at least partially translucentlight transmitting plate having an upper surface, a lower surface andside surfaces, said light transmitting plate being substantially hardand non-deformable; one or more light transmitting cavities projectinginto said lower surface of said plate, said one or more cavities eachhaving an arcuate dome-shaped sidewall so that said cavities arehemispherical or hemi-ellipsoid in shape, said sidewall of said one ormore cavities forming one or more plate-cavity interfaces; a reflectorcovering at least a portion of said plate's lower surface and said oneor more cavities; and a light source for communicating light throughsaid plate; said one or more interfaces being at least partiallytranslucent for allowing light transmitted through said plate to refractthrough said interface into said cavity, and said cavity being at leastpartially translucent to permit light refracted into said cavity toreflect off said reflector to again refract through said interface totravel upwardly through said plate to transmit light from said plate'supper surface.
 2. The light guide of claim 1 wherein said interface ispartially reflective so as to reflect light from said light sourceupwardly through said plate to transmit light from said plate's uppersurface.
 3. The light guide of claim 1 wherein said reflector coverssaid side surfaces.
 4. The light guide of claim 1 wherein said reflectorcovers said top surface except in places where light is to be emitted.5. The light guide of claim 1 wherein said reflector is white, lightgrey, silver, metallic silver or metallic gold.
 6. The light guide ofclaim 1 wherein one or more of said cavities are filled with air.
 7. Thelight guide of claim 1 wherein one or more of said cavities are filledwith a translucent colored material.
 8. The light guide of claim 1wherein one or more of said cavities are filled with a translucentphosphoric material.
 9. The light guide of claim 1 wherein saidreflector includes a phosphoric material.
 10. A lighted keyboardcomprising: one or more light transmitting hard non-deformable keysmembers; an at least partially translucent light transmitting plateunderlying and separate from said key members having an upper surface, alower surface and side surfaces; one or more light transmitting cavitiesprojecting into said lower surface of said plate, said one or morecavities each having an arcuate dome-shaped sidewall so that saidcavities are hemispherical or hemi-ellipsoid in shape, said sidewall ofsaid one or more cavities forming one or more plate-cavity interfaces; areflector covering at least a portion of said plate's lower surface andsaid one or more cavities; and a light source for communicating lightthrough said plate; said one or more interfaces being at least partiallytranslucent for allowing light transmitted through said plate to refractthrough said interface into cavity, and said cavity being at leastpartially translucent to permit light refracted into said cavity toreflect off said reflector to again refract through said interface totravel upwardly through said plate to transmit light from said plate'supper surface to illuminate said key members.
 11. The lighted keyboardof claim 10 wherein said interface is partially reflective so as toreflect light from said light source upwardly through said plate totransmit light from said plate's upper surface to illuminate said keymembers.
 12. The lighted keyboard of claim 10 wherein said reflectorcovers said side surfaces.
 13. The lighted keyboard of claim 10 whereinsaid reflector covers said top surface except in places where light isto be emitted.
 14. The lighted keyboard of claim 10 wherein saidreflector is white, light grey, silver, metallic silver or metallicgold.
 15. The lighted keyboard of claim 10 wherein one or more of saidcavities are filled with air.
 16. The lighted keyboard of claim 10wherein one or more of said cavities are filled with a translucentcolored material.
 17. The lighted keyboard of claim 10 wherein one ormore of said cavities are filled with a translucent phosphoric material.18. The lighted keyboard of claim 10 wherein said reflector includes aphosphoric material.